With rapid advancement of the fabrication technology of a thin film transistor liquid crystal display (TFT-LCD), the LCD is largely applied in various electronic products such as a Personal Digital Assistant (PDA) device, a notebook computer, a digital camera, a video camera, and a mobile phone due to the fact it has advantages of smaller size, lighter weight, lower power consumption and low radiation. Moreover, since the related manufacturers aggressively invest in research & development and employ large-scale fabricating equipment, the quality of the LCD is unceasingly improved and the price thereof is continuously decreased. This promptly broadens the applied fields of the LCD.
Since the LCD is not a light-emitting display apparatus, it performs a display function with the aid of a back light module. Please refer to FIG. 1 illustrating a sectional view of the back light module 10. The back light module 10 comprises a light guiding plate 11, a reflective plate 12, a lamp 13, a plurality of optical thin films 14 and a frame 15. The light guiding plate 11 and these optical thin films 14 are made of acrylic materials by injection or extrusion. Patterns as diffusion dots 16 for scattering light are formed on the bottom surface of the light guiding plate 11 and the surface of the optical thin films 14 for improving the brightness and the viewing angle of the LCD. The reflective plate 12 is disposed beneath the light guiding plate 11 and can reflect the light coming out from the light guiding plate 11 to return the light to the light guiding plate 11 for increasing the utilization of light. The lamp 13 is mounted at one side of the light guiding plate 11 and transmits lights into the light guiding plate 11 via one end of the the light guiding plate 11. The lamp 13 is generally composed by a cold cathode fluorescent lamp (CCFL). The frame 15 is mounted at the bottom and the sides of the back light module 10 for protecting the back light module 10 and the elements therein.
U.S. patent application Ser. Nos. 09/766,774 and 09/766,914 disclose two inventions relating to methods and apparatuses for patterning the bottom surface of a light guiding plate. In the disclosure, a plurality of pins of a V-cutter are inserted into the surface of the light guiding plate in a certain depth. A driver is used to drive the V-cutter in motion relative to the light guiding plate in a certain direction, so that a plurality of V-shaped grooves are formed by the pins on the surface of the light guiding plate. The pattern density of the grooves on the surface of the light guiding plate is gradually increased from one end nearer the lamp to the other end far away from the lamp, so that the uniformity of the light dispersed from the light guiding plate is increased.
However, the light guiding plate is fixed to a predetermined position in the prior art and a plurality of the V-shaped grooves are formed on the surface of the light guiding plate by driving the cutter. The pattern quality of these grooves is affected by the cutter due to vibration during the continuous scraping process. Moreover, the pins are fixed to the conventional cutter, the pattern of these grooves formed by the cutter is also fixed. The shape, density, or depth of grooves formed by the cutter are fixed. Sometimes, U-shaped grooves might be better than V-shaped grooves for some kinds of light guiding plates. In addition, the density and depth of these grooves may need to be adjusted because of different materials of the light guiding plates or non-uniform brightness of lamps. However, the conventional device for patterning light guiding plates cannot provide the above-mentioned functions, and thus affects the quality of the back light module.
In view of the above, those skilled in this art endeavor to improve the apparatus for patterning the optical elements such as a light guiding plate and an optical film, etc. so as to form patterns on the optical element with better quality, and thus to solve the problems occurred in the prior art.